Pregnancy induced hypertension (PIH) is a major disease of the obstetrical population and is associated with significant maternal and infant morbidity and mortality. Effective early screening tests for PIH are desirable but most of those currently available (e.g. the roll-over test, simple blood pressure measurements) have very poor positive predictive value. Doppler ultrasound has been suggested as a non-invasive screening test. The present study consists of two parts: 1) A series of experiments in pregnant ewes to investiagate the relationship between Doppler waveforms and uterine and umbilical artery resistance and blood flow. 2) A clinical study to evaluate the efficacy of Doppler ultrasound in the early detection of PIH. The animal experiments will be performed on 10 pregnant Dorset ewes (100 - 120 day gestation). Following anesthesia, laparotomy will be performed and pressure and flow meters inserted surgically. Electromagnetic and Doppler probes will be placed around the uterine (5 ewes) or umbilical (5 ewes) arteries. Graded embolization of the placenta by microspheres will alter the placental resistance during the experiment. Following each flow embolization, arterial and venous pressures and resistance will be measured. At the same time, Doppler spectra from either the uterine or umbilical artery will be obtained from two devices: a probe placed around the artery and a commercially available Dopper machine. The Doppler spectra will be analyzed to determine indices that are the most strongly correlated with resistance and flow. Comparison between the spectra obtained by the two devices will be made. The indices to be used in the clinical study wll be determined by these experiments. The clinical study consists of a sample of clinical patients (n = 3600) seen at the Thomas Jefferson University Hospital Department of Obstetrics and Gynecology outpatient facility. These patients will have Doppler ultrasound screening at 24 and 30 weeks of gestation. Measures of uteroplacental and umbilical Doppler flow waveforms will be taken. In addition, blood pressure, maternal anthropometry and medical history will be recorded. At 30 weeks a supine pressor test will be performed. Data will be gathered during routine obstetrical exams as well as during hospital admissions. At birth, data on labor and delivery will be collected by hospital staff using special forms. Dubowitz exams, phenotype screening, and anthropometry will be carried out on all infants. Sensitivity, specificity, positive and negative predictive value for Doppler waveforms in predicting negative outcome will be computed. Comparisons will be made to other simple clinical indicators of PIH. In addition, comparisons between sensitivities of umbilical and uteroplacental waveforms at 24 and 30 weeks will be made.